Pakistan's interior minister on Wednesday warned an anti-government Muslim cleric and thousands of protesters camped out near parliament to disperse, saying they were at risk of attack by militants.
Rehman Malik said authorities had learned militants might be planning to target the crowd, and that the cleric, Muhammad Tahirul Qadri, would be held responsible for any attacks.
"The best commandos are with me today," Malik told a news conference, saying security forces could take action against Qadri within the next two days to prevent "expected terrorism".
"I hope that he listens to me."
Qadri, who backed a military coup in 1999, is calling for the immediate resignation of the government and the installation of a caretaker administration to oversee electoral reforms.
The government was rocked on Tuesday by a Supreme Court order for the arrest of Prime Minister Raja Pervez Ashraf within 24 hours on suspicion of corruption.
Qadri's appearance at the forefront of Pakistan's political scene has fuelled speculation that the army, which has a long history of involvement in politics, has tacitly endorsed his campaign in an effort to pile more pressure on a government it sees as inept and corrupt.
Qadri and the military deny this.
Pakistan's information minister Qamar Zaman Kaira said political leaders would not bow to Qadri's demands.
"All political parties are happy with the Election Commission and elections will happen on time," he said.
He added that elections would take place as scheduled between May 5 and 15.
The opposition Pakistan Muslim League led by former prime minister Nawaz Sharif also rejected Qadri's call for the military to play a role in the formation of a caretaker government to oversee the run-up to elections.
"Tahirul Qadri is working on somebody's agenda to derail democracy in Pakistan and we reject all of his demands," Sharif told a news conference.
Qadri's appeal has cast fresh uncertainty over the government's effort to become the first civilian Pakistani administration to complete a full term.
The military has ruled Pakistan for over half of its 65 years since independence. Current chief General Ashfaq Kayani has vowed to keep the military out of politics.
Prime Minister Ashraf remained a free man on Wednesday since officials said the National Accountability Bureau (NAB), which would carry out the arrest, had not yet received direct orders.
The officials said the NAB chief would go the Supreme Court on Thursday to discuss the issue.
The ruling coalition, led by the Pakistan People's Party, has a majority in parliament and its lawmakers can simply elect another prime minister if Ashraf is ousted.
In June, Ashraf replaced Prime Minister Yusuf Raza Gilani, who was disqualified by the Supreme Court in a previous showdown between the government and the judiciary.